Silicon anode comprising coated silicon particles, methods for its production and its use

Abstract

The invention relates to a silicon anode, in particular for use in electrochemical primary cells with alkali electrolytes, in the form of a three-dimensional moulded body with an outer surface and an inner surface, wherein the three-dimensional moulded body comprises silicon particles with a particle size of 1 nm to 200 micrometer, which have contact points, in particular made of silicon, to neighbouring silicon particles, with the neighbouring silicon particles being integrally connected to one another via the contact points, in particular, the connection between the silicon particles is made of silicon, wherein, on at least one part of its outer surface, the three-dimensional moulded body has a coating of a conductive metal alloy or of a metal for electrical contacting. The invention also relates to a method for producing the silicon anode, and to the use of same in a primary cell or a battery comprising a plurality of primary cells.

Description

[0001] Silicon anode comprising coated silicon particles, process for its production and its use

[0002] The invention relates to a silicon anode, in particular for use in electrochemical primary cells with alkaline electrolyte, in the form of a three-dimensional shaped body with an outer surface and an inner surface, wherein the three-dimensional shaped body comprises silicon particles with a particle size of 1 nm to 20 micrometers, which have contact points, in particular made of silicon, to adjacent silicon particles, via the contact points the adjacent silicon particles are materially connected to one another, in particular the connection between the silicon particles is made of silicon, wherein the three-dimensional shaped body has a coating of a conductive metallic alloy or a metal for electrical contacting on at least part of its outer surface and optionally part of the inner surface.Furthermore, the invention relates to a method for producing the silicon anode and the use thereof in a primary cell or a battery comprising a plurality of primary cells.

[0003] Due to the growing demand for e-mobility in local public transport through electric cars, electric bicycles, and electric buses, as well as the increasing use of decentralized power generation, there is a huge demand for environmentally friendly batteries whose components should be both infinitely available and infinitely recyclable, environmentally friendly, and / or reusable. Silicon is a raw material with unlimited availability on Earth. Furthermore, battery components must be available at low cost.

[0004] Furthermore, it is known that electrical energy can be generated by continuously supplying fuel to fuel cells that have a galvanic cell in the presence of an oxidizing agent. In principle, this principle is also conceivable for silicon-air batteries. Furthermore, conventional silicon-containing lithium-ion secondary batteries are in daily use worldwide.

[0005] The object of the invention was to provide a silicon anode for a silicon-containing galvanic cell, in particular a primary cell, in an economical manner, which can provide a good power density and a high starting voltage. A further object was to provide a silicon anode which is preferably free of lithium, where preferably free of lithium means that the lithium content in the silicon anode is less than 1 wt. % based on the total composition of the silicon anode. A primary cell equipped with the silicon anode preferably has less than 0.1 wt. % lithium in the total composition of the primary cell in the charged state. The lithium content in the electrode material of the anode in the charged state should preferably be less than 0.1 wt. %.A further object was to provide an anode comprising reactants and / or reaction products that originate from recycling processes, are byproducts, and / or can be reused in recycling processes. These objects were achieved by a silicon anode according to claims 1 and 15, a method for its production according to claim 13, and the use according to claims 16 and 17. Preferred embodiments are disclosed in the subclaims and in detail in the description.

[0006] The invention relates to a silicon anode, in particular for use in electrochemical primary cells with alkaline electrolyte, wherein the silicon anode is a three-dimensional shaped body with an outer surface and an inner surface, and wherein the three-dimensional shaped body comprises silicon particles with a particle size of 1 nm to

[0007] 30 micrometers, and the silicon particles are materially bonded to one another at contact points with neighboring silicon particles, in particular the material bond is formed by silicon, wherein the three-dimensional shaped body has a coating of a conductive metallic alloy or a metal for electrical contacting on at least part of its outer surface.

[0008] According to the invention, the silicon particles are bonded together by means of the silicon in the silicon particles. It is preferred if a) the bonded silicon particles are i) fused and / or ii) sintered and / or iii) pressed together, or b) the bond is formed at the contact points of the silicon particles by silicon material in the silicon particles, by the silicon particles being i) fused and / or ii) sintered and / or iii) pressed together.

[0009] According to a preferred embodiment, the silicon anode has a shaped body having a density of 0.1 g / cm 3 up to 2.3 g / cm 3 More preferably, the shaped body has a density of 0.5 g / cm 3 up to 2.1 g / cm 3 preferably from 0.5 to 1.8 g / cm 3 , more preferably from 1.3 to 1.8 g / cm 3 .

[0010] Preferably, the outer surface of the shaped body is formed by the outwardly directed surfaces of the silicon particles and optionally the outwardly directed surfaces of the contact points and the inner surface of the shaped body is formed by the inwardly directed surfaces of the silicon particles and optionally the inwardly directed surfaces of the contact points.

[0011] Preferably, the outer surface of the shaped body formed by the silicon particles is at least 5%, preferably 10%, and particularly preferably at least 15% larger than the surface of the enveloping body of the shaped body. The enveloping body is the simple geometric body of the shaped body that lies in the planes of the surfaces forming the shaped body.

[0012] According to a particularly preferred embodiment, the silicon anode has a shaped body selected from polyhedrons, in particular Platonic solids, spheres, hemispheres, cones, in particular selected from prisms, cylinders, cuboids, and cubes, with a plate-like shaped body being particularly preferred. The shaped body can also be in the form of a tablet, briquette, rod-shaped, or in any conceivable three-dimensional geometry. The shaped body is particularly preferably a flat surface element, in particular a rectangular surface element of a defined height, in particular a cuboid, optionally with rounded corners. Likewise, the shaped body is preferably a flat plate or a flat disc, preferably a rectangular plate or disc, optionally with rounded edges, or a round plate or disc. All geometries in between are possible.

[0013] The shaped body of the silicon anode can be a flat shaped body of defined height, in particular as a flat plate or flat disc, wherein the plate or disc has a round, rectangular, or rectangular with at least one rounded edge, opposite front and rear sides. In particular, the plate or disc has a rectangular cross-section, optionally with rounded edges. The front side, when installed in a primary cell, will face an electrolyte, and the rear side can have a coating with a conductive metallic alloy or a metal for electrical contacting. In an equally preferred alternative, both the front and the rear side will face the electrolyte, wherein in this case in particular the coating is provided in the region of a side surface and / or on the outer surface in a region of the front and / or rear side in the region of the outer circumference of the shaped body.

[0014] Furthermore, it is preferred if the three-dimensional shaped body of the silicon anode is in the form of a substantially flat plate or disc, wherein the plate or disc i) has a front side and a rear side opposite the front side, wherein the front side will face an electrolyte and the rear side has at least partially a coating with a conductive metallic alloy or a metal for electrical contacting, or the plate or disc ii) has a front side and a rear side opposite the front side and one or more circumferential side surface(s) connecting the front and rear sides, wherein the front and rear sides will at least partially face an electrolyte and a region of the side surface(s) and optionally a region of the front and / or rear side that adjoins the side surface(s),has a coating with a conductive metallic alloy or metal for electrical contacting, in particular the contact area of ​​the front and / or back is 1 / 3 to 1 / 5000 of the outer surface of the front and / or back.

[0015] Preferably, at least one side surface and optionally an area of ​​the front and / or back side adjacent to this side surface, which has a coating of the plate with a conductive metallic alloy or a metal for electrical contacting, in particular the area of ​​the front and / or back side is 1 / 10 to 1 / 1000 of the outer surface of the front and / or back side.

[0016] According to the invention, the coating is applied with a soft solder or hard solder, more preferably with a precious metal or precious metal-containing alloy, particularly preferably with gold. Furthermore, it is preferred if the mass ratio of the silicon anode molded body to the coating is 1,000,000:1 to 10:1, in particular from 100,000:1 to 100:1, particularly preferably 10,000:1 to 50:1.

[0017] The coating preferably has a layer thickness of 10 nm to 5 mm, preferably 100 nm to 5 mm.

[0018] The coating of the conductive metallic alloy or a metal for electrical contacting preferably comprises elements from groups 3 to 11 of the Periodic Table, preferably groups 8 to 11, and particularly preferably groups 3 to 11 of periods IV, V, and VI of the Periodic Table (main groups 3 to 11). Elements from groups 8 to 11 and periods V and VI are particularly preferred. Precious metals, including gold, ruthenium, rhodium, osmium, iridium, platinum, and / or silver, are preferred.

[0019] Furthermore, the silicon anode can preferably have an at least partial inhibition coating on the outer and / or inner surface of the shaped body to inhibit the corrosive dissolution of the silicon anode in a strongly alkaline, aqueous electrolyte. The silicon particles are advantageously silanized and / or coated with siloxanes or covalently bonded. Advantageously, the shaped body is at least partially provided or can be provided with at least one functional silane, functional siloxane, a mixture of functional silanes, a mixture of functional silanes and functional siloxanes, and / or a mixture of siloxanes on at least part of its outer and / or inner surface, which preferably does not have a coating with a conductive metallic alloy or a metal for electrical contacting.The silanes and / or siloxanes can be covalently bonded, adsorbed or electrostatically arranged on or at the respective surface.

[0020] Preferred functional silanes include alkyltrialkoxysilanes, dialkyldialkoxysilanes, (polyalkylene oxide)alkylsilanes, glycidylalkyltrialkoxysilanes, glycidylalkyl(alkyl)dialkoxysilanes, as well as their hydrolysis and optionally condensation products alkylsiloxanes, dialkylsiloxanes,

[0021] (Polyalkylene oxide)alkylsiloxanes, glycidylalkylsiloxanes, glycidylalkyl(alkyl)siloxanes. The respective alkyl groups can be linear, branched and / or cyclic and can comprise 1 to 24 C atoms, preferably 1 to 10 C atoms, particularly preferably 1 to 8 C atoms. The alkoxy groups are preferably selected from methoxy, ethoxy, propoxy and

[0022] Butoxy. Furthermore, all hydroxy-functional silanes of the aforementioned silanes are included, which are obtainable by hydrolysis of the respective alkoxysilanes.

[0023] The silanes and / or siloxanes can preferably be covalently bonded to surfaces containing Si-O groups via one or two Si-O bonds in the alkaline electrolyte. The silanes and / or siloxanes preferably contain two alkyl groups. It may be preferred if the silanes are functionalized with groups that either cause significant steric hindrance to the hydroxide ions, preventing them from freely penetrating the surface of the silicon anode, or if the functional groups comprise (polyalkylene oxide)alkyl groups, which can flexibly cover the surface of the silicon anode and thus inhibit corrosion for a certain period of time.

[0024] Likewise, it is preferred if, in addition or alternatively, the aqueous alkaline electrolyte contains a polyalkylene oxide or a mixture of polyalkylene oxides. It is preferred if the alkylenes are selected from divalent alkylenes comprising 1 to 6 carbon atoms, and the divalent alkylenes are preferably selected from methylene, ethylene, n-propylene, isopropylene, and butylene. Furthermore, it is preferred if the polyalkylene oxide is selected from HO(C2H4O). n H with n greater than or equal to 4, R 1 O(C2H4O)niR 2 with R 1 and R 2 each independently selected from -H, -alkyl, -C=O-alkyl with alkyl each independently having 1 to 6 C atoms, where R 1 or R are not equal to H, with n1 = greater than or equal to 4, HO(C3HeO) m H with m greater than or equal to 4, R 3 O(C3HeO)miR 4 with R 3 and R 4each independently selected from H, alkyl, -C=O-alkyl, with alkyl each independently having 1 to 6 C atoms, with m1 greater than or equal to 4, where R 3 or R 4 are not equal to H, polyethers of the aforementioned polyalkylene oxides comprising ethylene oxide and propylene oxide units and mixtures of polyalkylene oxides comprising at least two different polyalkylene oxides.

[0025] Preferred compounds containing polyalkylene oxide groups, in particular comprising polyalkylene oxide groups, can preferably have a molecular weight of 200 g / mol to 35,000 g / mol, preferably 200 to 1500 g / mol. It is further preferred if the average molecular weight is from 200 g / mol to 1500 g / mol.

[0026] A silicon anode according to the invention can advantageously be provided with a film or coating comprising polyalkylene oxide. Further preferred is a kit comprising at least one silicon anode in a polyalkylene oxide in a disposable or reusable container.

[0027] The invention also relates to a silicon anode which comprises silicon particles with an at least bimodal particle size distribution, wherein the silicon particles comprise i) silicon particles with a particle size of 1 nm to 50 nm, and ii) silicon particles with particle sizes of 60 to 200 nm. Alternatively, the particle size distribution can comprise i) silicon particles with a particle size of 1 nm to 500 nm, and ii) silicon particles with particle sizes of 1 to 30 micrometers. Alternatively or additionally, the particle size distribution can comprise i) silicon particles with a particle size of 1 nm to 25 nm, and ii) silicon particles with particle sizes of 30 nm to 100 micrometers.

[0028] Preferably, contact points are formed between silicon particles with a particle size of 1 nm to 30,000 nm by i) fusing and / or ii) sintering and / or iii) pressing particles of different particle sizes together. Preferably, contact points are formed between silicon particles with a particle size i) of 1 nm to 500 nm and optionally a particle size ii) of 510 nm to 30 micrometers by i) fusing and / or ii) sintering and / or iii) pressing particles of different particle sizes together. Alternatively, the particle size distribution of the silicon particles can be trimodal and comprise particles i) from 1 nm to 500 nm, ii) from 800 nm to 5 micrometers and iii) from 7 micrometers to 30 micrometers, wherein the silicon particles are preferably materially connected to one another via contact points. According to the invention, materially connected is preferably understood to mean integrally connected.Therefore, the silicon particles are preferably integrally connected to each other via the contact points.

[0029] According to the invention, the silicon particles of the shaped body of the silicon anode particularly preferably have a content of iron, zinc, potassium, aluminum, carbon, calcium, optionally titanium, optionally copper of in each case greater than or equal to 0.01 mg / kg. The invention likewise provides a shaped body comprising silicon particles which have an iron and aluminum content of greater than or equal to 0.02 mg / kg. Furthermore, the invention provides a shaped body comprising silicon particles and optionally particles containing carbon and silicon and optionally particles of at least one allotropic carbon modification, wherein the silicon particles, in particular the silicon anode, have an iron content of greater than or equal to 0.02 mg / kg. The particles containing carbon and silicon and particles having at least one allotropic carbon modification can include carbon black, spherical nanoparticles comprising graphite, graphite and polycyclic carbon.These particles preferably have a diameter of greater than or equal to 10 nm, in particular between 10 nm and 300 nm. The surface area of ​​these particles is preferably at least 1 m. 2 / g up to 600 m 2 / g. The carbon- and silicon-containing particles preferably comprise silicon carbide, and / or the particles of at least one allotropic carbon modification comprise diamond, polycyclic carbon modifications, graphite, fullerene, and graphene. Diamond can originate from a wire-sawing recycling process.

[0030] The invention further relates to a silicon anode comprising silicon particles, in particular the silicon anode, with an iron content of greater than or equal to 0.02 mg / kg, preferably greater than or equal to 0.05 mg / kg to less than or equal to 2500 mg / kg, preferably greater than or equal to 5 mg / kg to less than or equal to 250 mg / kg. Particularly preferably, the iron content originates at least partially from abrasion of steel products, such as steel-containing saws. The advantage of the iron content in the silicon anode and / or silicon particles is that iron does not corrode at an alkaline pH, and corrosion is very effectively prevented, in particular, at a pH of 9.2 to 9.5. For steel, the protective effect is most effective at a pH of 9.8. In this way, the iron content in the silicon anodes and / or silicon particles can efficiently reduce corrosion in alkaline electrolytes, particularly in aqueous KOH. Consequently, the anode efficiency can be increased.Anode efficiency depends on the oxidation of the silicon on the surface and can be improved, among other things, by increasing the iron content. The focus for increasing anode efficiency, discharge performance, and thus the service life of the silicon anodes and / or silicon particles is corrosion inhibition.

[0031] According to a further embodiment, the subject matter of the invention is a silicon anode for use in an electrochemical primary cell. A primary cell, in particular an electrochemical primary cell, is understood to be a primary battery or primary cell that is intended to be discharged once, whereby this single discharge can also take place in several steps. A single discharge is understood to be the state after current has been drawn until the capacity is completely exhausted or until the voltage of the primary cell falls below a certain level. A primary cell is thus defined as an electrochemical cell that can be converted once, optionally in several steps, from an output voltage (Vcharges), at which the cell is considered charged, to a discharge voltage (Vcharges), and this process is irreversible.A primary cell can thus be used and disposed of, and cannot be recharged with electricity for reuse like a secondary cell. A silicon anode according to the invention in a primary cell is thus consumed or dissolved over its lifetime due to corrosion by the electrolyte, and is particularly unavailable for recharging.

[0032] A particularly preferred alternative or additional anode material can comprise Siridion®-Black. According to an alternative, the anode material can comprise silicon-containing particles with a carbon content, in particular with a carbon content of 1 to less than 10 wt.% in the total content of the silicon-containing particles. Preferred anode materials can comprise mixtures of silicon particles without a carbon content and silicon particles with a carbon content. The silicon particles mentioned according to the invention can also be present as mixtures comprising defined fractions of silicon particles with qualitatively different compositions.

[0033] According to one embodiment, the shaped body preferably comprises silicon particles and optionally carbon and silicon-containing particles and optionally particles of at least one allotropic carbon modification, wherein the silicon particles each independently of one another, in particular the silicon anode, each independently of one another have a content of iron, potassium, zinc, aluminum, carbon, calcium, optionally titanium, optionally copper, optionally oxygen of greater than or equal to 0.01 mg / kg. Furthermore, it may be preferred if the content in the silicon particles, in particular the silicon anode, is:

[0034] -Iron greater than or equal to 0.05 mg / kg,

[0035] - Aluminium greater than or equal to 0.01 mg / kg,

[0036] - Oxygen greater than or equal to 0.01 mg / kg,

[0037] - Carbon greater than or equal to 0.01 mg / kg,

[0038] - Potassium greater than or equal to 0.01 mg / kg,

[0039] - Calcium greater than or equal to 0.01 mg / kg,

[0040] - and optionally titanium greater than or equal to 0.001 mg / kg,

[0041] - and optionally copper greater than or equal to 0.001 mg / kg.

[0042] Silicon anodes can comprise silicon particles with i) an iron content of greater than or equal to 0.02 mg / kg, preferably greater than or equal to 0.05 mg / kg, and / or ii) the silicon anode comprises iron-containing particles, wherein the iron-containing particles have an iron content of greater than or equal to 90 wt.% with respect to the total composition of the iron-containing particles, wherein the iron-containing particles preferably comprise a steel alloy. The iron-containing particles with an iron content of greater than 90% can, for example, originate from a recycling process, e.g., from the processing of the sawing suspension from a wafer wire sawing process. Furthermore, the silicon particles or the silicon anode can have a content of: - iron greater than or equal to 5 mg / kg,

[0043] - Carbon greater than or equal to 5 mg / kg,

[0044] - Aluminium greater than or equal to 0.5 mg / kg,

[0045] - Oxygen greater than or equal to 0.5 mg / kg,

[0046] - Potassium greater than or equal to 0.5 mg / kg,

[0047] - Calcium greater than or equal to 5 mg / kg,

[0048] - and optionally titanium greater than or equal to 0.01 mg / kg,

[0049] - and optionally copper greater than or equal to 0.05 mg / kg.

[0050] The silicon particles can include primary particles, amorphous silicon particles, and mono- or polycrystalline silicon particles. Primary particles are particles that form in a thermal process for producing silicon particles and subsequently clump together to form aggregates and / or agglomerates. The primary particles typically have a diameter of 1 to 200 nm, while the aggregates and / or agglomerates can have a size of 300 to 30 micrometers in at least one dimension. A preferred particle size distribution for amorphous silicon particles can be from 1 nm to 700 nm, in particular from 10 nm to 500 nm, and the mono- to polycrystalline particles have a particle size distribution of 800 nm to 30 micrometers, in particular from 800 to 30 micrometers.Furthermore, it may be preferred if the mono- to polycrystalline silicon particles are bimodal with silicon particles in the range from 800 nm to 9 micrometers and from 13 to 20 micrometers.

[0051] Likewise, the silicon particles or other particles with polymerizable monomers can be present in a composition that is shaped and polymerized and optionally subsequently sintered or pyrolyzed.

[0052] Alternatively, a silicon anode with a molded body can be obtained using a process such as powder injection molding. In powder injection molding, silicon particles are mixed with an organic binder and then molded into a shape on an injection molding machine. The binder is then removed and the component is sintered at high temperature in a furnace. Alternatively, a silicon anode with a molded body can be obtained by solid-phase sintering or liquid-phase sintering with a mixture of the silicon particles and a component with a lower melting point, which can preferably be removed by pyrolysis or heating.

[0053] The invention also relates to a process for producing a silicon anode and a silicon anode obtainable by the process, the process comprising the steps

[0054] Providing silicon particles with a particle size of 1 nm to 200 micrometers, in particular with an at least bimodal particle size distribution comprising a) i) particles with a particle size of 1 nm to 50 nm, and ii) particles with particle sizes of 60 to 200 micrometers, or b) i) particles with a particle size of 1 nm to 500 nm, and ii) particles with particle sizes of 1 to 30 micrometers, and A) optionally producing a composition comprising the silicon particles and at least one polymerizable monomer or a mixture of polymerizable monomers, and forming the composition into a blank of the three-dimensional molded body, such as a green body, or

[0055] B) forming the silicon particles into a blank of the three-dimensional shaped body, and

[0056] - Heating the blank of the three-dimensional molded body, optionally under overpressure, optionally cooling the resulting molded body, and

[0057] - Obtaining the three-dimensional shaped body with an outer surface and an inner surface comprising the silicon particles, wherein in particular the three-dimensional shaped body comprises silicon particles with a particle size of 1 nm to 30 micrometers,

[0058] - coating the three-dimensional shaped body comprising the silicon particles on at least part of its outer surface with a coating of a conductive metallic alloy or a metal for electrical contacting, and

[0059] Obtaining a silicon anode comprising a three-dimensional shaped body comprising the silicon particles, with a coating of a conductive metallic alloy or metal for electrical contacting on at least part of its inner and / or outer surface. According to another embodiment, mesh electrodes, e.g., iron mesh, steel mesh, carbon mesh, silver mesh, etc., can be used as contact carriers for the silicon particles by embedding the mesh electrode in silicon particles and further processing, for example, according to A) or B).

[0060] According to a preferred embodiment, silicon particles with a particle size of 1 nm to 30 micrometers originating from a reprocessed sawing suspension in the wafer wire sawing process are used, in particular with a bimodal particle size distribution of the silicon and iron-containing particles.

[0061] According to one embodiment, the heating of the blank is carried out under pressure, in particular with greater than 1.5 bar, preferably with greater than or equal to 10 bar, more preferably with greater than or equal to 50 to 500 bar, such as at 180 bar with + / - 20 bar.

[0062] The blank is preferably heated below the melting point of the silicon particles. The silicon particles can be n- or p-doped and / or contain the aforementioned metals and / or carbons. The blank is advantageously heated to a temperature greater than or equal to 500°C until it melts, preferably from greater than or equal to 500°C to just below the melting temperature of the silicon particles. A preferred temperature range is from 500 to 1350°C, more preferably from 550 to 1100°C. Heating, optionally under excess pressure, is preferably carried out for 2 seconds to 2 hours, preferably from 60 seconds to 600 seconds, in particular from 30 to 300 seconds.

[0063] If no mesh electrode was used, the hot or cooled molded body can be provided with a contact layer or coating. The contact layer / coating can advantageously be applied by sputtering. According to one embodiment, the molded body of the silicon anode has a coating of at least two layers of a conductive metallic alloy or metal for electrical contacting on at least part of its outer surface. Preferably, two to 20 layers are sputtered on.

[0064] Alternative coating methods include dipping, spraying, etc. with a solder material or brazing agent known to those skilled in the art.

[0065] According to one embodiment, it is preferred that the silicon particles used in the process have a content of iron, zinc, potassium, oxygen, aluminum, carbon, calcium, optionally titanium, optionally copper of each greater than or equal to 0.01 mg / kg.

[0066] The invention relates to an aqueous, alkaline electrolyte composition containing 2.0 to 99.0 wt.% water, a content of 0.001 to 40 wt.%, in particular 10 to 40 wt.%, of alkali hydroxide, based on the total composition of 100 wt.%. Optionally, the electrolyte composition can comprise a corrosion inhibitor for the silicon anode, in particular with 0.001 to 20 wt.% based on the total composition. Particularly preferably, an alkaline electrolyte composition contains 2 to 5 mol / liter of alkali hydroxide in the total composition, particularly preferably 4 mol / liter with plus / minus 0.5 mol / liter of alkali hydroxide.

[0067] The alkali metal hydroxide can be selected from NaOH and KOH, and optionally other alkaline soluble salts, such as alkaline earth metal hydroxides, basic metal oxides, or organic bases. The electrolyte composition preferably comprises an alkali metal hydroxide selected from KOH and NaOH. Furthermore, the water is preferably distilled water.

[0068] The invention also relates to the use of silicon particles comprising a content of iron, zinc, potassium, oxygen, aluminum, carbon, calcium, optionally titanium, optionally copper, each independently greater than or equal to 0.01 mg / kg for producing silicon anodes comprising a three-dimensional shaped body with an outer surface and inner surface, wherein the three-dimensional shaped body comprises silicon particles with a particle size of 1 nm to 200 micrometers, and the silicon particles are integrally bonded to one another at contact points with adjacent silicon particles, in particular by means of silicon material of the silicon particles, wherein the three-dimensional shaped body preferably has a coating of a conductive metallic alloy or a metal for electrical contacting on at least part of its outer surface.

[0069] The invention further relates to the use of a silicon anode as an electron-providing fuel, in particular for use as an electron source in an anode of a primary cell. The invention also relates to the use of silicon anodes as an anode in an electrochemical primary cell or as an anode in at least one primary cell of a multi-cell battery, wherein the battery comprises at least two to 15,000 interconnected primary cells, preferably two to 15,000 of the interconnected primary cells are connected in series, preferably two to 1,000 primary cells are connected in series, wherein in particular the silicon anode forms the anode in all primary cells.

[0070] The silicon anode of the present invention can advantageously be used in a primary cell in the form of i) a flat disc or plate with the backside provided with the coating, or ii) as a plurality of discs or plates combined in at least one stack in an anode and used in a primary cell. The primary cells can be connected to form multi-cell batteries. Batteries with at least two to 15,000 interconnected primary cells are preferred; the two to 1,000 interconnected primary cells are preferably connected in series.

[0071] The coating of the conductive metallic alloy or of a metal for electrical contacting comprises elements from groups 3 to 11, preferably groups 8 to 11, and particularly preferably groups 3 to 11 of periods IV, V and VI of the Periodic Table (main groups 3 to 11), particularly preferred are the elements from groups 8 to 11 and periods V and VI. Preference is given to noble metals comprising gold, ruthenium, rhodium, osmium, iridium, platinum and / or silver. Further preference is given to alloys of gold and silver. The coatings can be applied from the gas phase after production of the shaped body or, alternatively, can be applied to the blank using a conventional printing process and then heated together with the blank in one step to obtain the silicon anodes.

[0072] Preferred primary cells of the invention are preferably free of lithium, whereby preferably free of lithium is understood to mean that the lithium content in the charged state in the primary cell, in particular comprising the anode, the cathode and the electrolyte, is less than or equal to 1 wt.%, in particular less than or equal to 0.1 wt.% in the primary cell, preferably the lithium content in the electrode material of the anode in the charged state is less than or equal to 0.1 wt.%. Electrochemical primary cells and in particular anodes for electrochemical processes with a lithium content below 1

[0073] % by weight, preferably less than or equal to 0.1 % by weight, are considered to be free of lithium and are referred to according to the invention as pure silicon cells or pure silicon anodes.

[0074] According to a preferred embodiment, the silicon, in particular the silicon particles, preferably the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are selected from elements of the 13th main group, in particular comprising boron, indium, aluminum and / or gallium, and from elements of the 15th main group, in particular comprising phosphorus, arsenic and / or antimony as well as elements of the iron group, particularly preferably boron, aluminum, phosphorus and / or iron. The elements of the 13th main group (new nomenclature: Group 13 of the Periodic Table) are electron acceptors of the new nomenclature. Elements of the 15th main group (new nomenclature: Group 15 of the Periodic Table) are used as electron donors. According to one embodiment, the silicon, in particular the silicon particles of the anode material, comprises dopants, wherein the dopants comprise greater than or equal to 1 element of the 15th main group per 10 6Silicon atoms and / or greater than or equal to 1 element of the 13th main group per 10 6 Silicon atoms are present, in particular greater than or equal to 1 element of the 15th main group per 10 4 Silicon atoms and / or greater than or equal to 1 element of the 13th main group per 10 4 Silicon atoms, determined using ICP-MS analysis (Inductive Plasma Discharge Mass Spectroscopy, which is described in detail on Wikipedia: https: / / de.wikipedia.org / wiki / Massenspektrometrie_mit_induktiv_gekoppeltem_Plasma). Alternatively, the analysis can also be performed using GD-MS (GDMS / GD-MS glow discharge mass spectroscopy with a Secondary Electron Multiplier (SEM) and / or Faraday detector, as per source: https: / / assets.thermofisher.com / TFS-Assets / CMD / brochures / BR-30066-GD-MS-ELEMENT- GD-PLUS-BR30066-EN.pdf). The Faraday detector is preferably used for measuring trace concentrations in the % range.

[0075] According to an alternative, preferred embodiment, the silicon, in particular the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are greater than or equal to 10 2 Atoms (approx. 100 ppm by weight, depending on the atomic weight of the dopant) of the 15th main group to 10 6 silicon atoms and / or greater than or equal to 10 2 Atoms of the 13th main group to 10 6 silicon atoms are present.

[0076] According to further preferred, alternative embodiments, the silicon, in particular the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are greater than or equal to 2*10 2 Atoms of the 15th main group to 10 6 Silicon atoms greater than or equal to 2*10 2 Atoms of the 13th main group to 10 6Silicon atoms are present. The above contents of dopants in the silicon of the anode material can be inhomogeneously distributed in the silicon, as well as the contents can be present integrally over the total amount of silicon in the anode material on average. To determine the above contents, a test quantity of 1 g of the test quantity is measured by GD-MS or ICPMS, whereby certain deviations can be determined between the two methods; preferably, an average value is determined. According to further preferred, alternative embodiments, the silicon, in particular the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are greater than or equal to 10 3 Atoms of the 15th main group to 10 6 silicon atoms and / or greater than or equal to 10 3 Atoms of the 13th main group to 10 6 silicon atoms.

[0077] According to further preferred, alternative embodiments, the silicon, in particular the amorphous silicon particles, of the anode material comprises dopants, wherein the dopants are greater than or equal to 10 19 Atoms of the 15th main group to 2*10 22 silicon atoms and / or greater than or equal to 10 19 Atoms of the 13th main group to 2*10 22 silicon atoms.

[0078] The silicon particles may comprise, at the atomic level, an alloy of silicon with at least one element of the 13th or 15th main group, wherein the at least one element of the 13th or 15th main group is most preferably greater than or equal to 0.5*10 21 atoms / cm 3and is selected from at least one electron donor and electron acceptor. The alloy of silicon at the atomic level with at least one element of main group 13 or 15 is present as an amorphous or crystalline phase. The silicon particles particularly preferably have a boron content of 10 ppm by weight to 2.5 wt.% in relation to the total content of 100 wt.% of the silicon particle, preferred is a content of 10 ppm by weight to 1.8, particularly preferred is 1.8 wt.% plus / minus 0.2 wt. Analogously, the silicon foil can have a boron content of 10 ppm by weight to 1.8 wt.% in relation to the total content of 100 wt.% of the silicon foil. Surprisingly, it has been found that the alloys of silicon and boron have an anti-corrosive effect, so that the service life of the primary cell is extended.

[0079] The invention relates to a silicon anode comprising silicon particles having a boron content of 10 ppm by weight to 1.8% by weight.

[0080] Furthermore, an economical cathode material is provided, which preferably comprises a physical mixture of manganese dioxide (MnO2) and a conductivity promoter. The optional content of the conductivity promoter in the electrodes of the primary cell can vary in the cathode and the anode. For manganese dioxide, a conductivity promoter content of approximately 5 to 65 wt.%, preferably 5 to 15 wt.%, is typical in the cathode material. In general, the conductivity promoter content can be from 5 to 60 wt.% in the cathode material. Alternatively, preferred contents can be in the range of 15 to 20 wt.% for a lower resistance, or 30 to 60 wt.% as an upper limit. The total cathode material always amounts to 100 wt.%.

[0081] The invention thus relates to at least one electrochemical primary cell which has an anode, a cathode, an electrolyte and at least one separator, wherein the separator separates the cathode and the anode from one another, and the cathode comprises manganese dioxide as material and optionally a carbon-containing conductivity promoter, wherein the anode comprises silicon as anode material and wherein the silicon is in the form of silicon particles and the silicon primary particles have a particle size between 1 nm and 3000 nm, and the primary particles are optionally substantially amorphous. It is particularly preferred if the silicon particles, and in particular the silicon primary particles, have a crystallinity of less than or equal to 20%, in particular 12%, in particular a crystallinity of less than or equal to 2%. Silicon primary particles with a crystallinity of less than 12%, preferably less than 2%, are considered amorphous.

[0082] Preferably, the silicon particles in the anode are present as aggregates and optionally the lithium content is less than or equal to 1 wt.% with respect to the silicon content of the anode of 100 wt.% of the primary cell, wherein the lithium content in the charged state of the primary cell is preferably less than or equal to 0.1 wt.%.

[0083] A powder is considered essentially amorphous if it is X-ray amorphous. A powder with a crystallinity of less than 20%, preferably less than 12%, and particularly preferably less than or equal to 2% is preferably considered X-ray amorphous. The degree of crystallinity can be determined using XRPD using the formula % crystallinity = (100 x A) / (A + B -C) where A = total peak area of ​​the reflections of the crystalline components of the diffractogram; B = total area below peak area A; C = air scattering, fluorescence, and instrument-related background area. Total peak area A including background directly below the narrow reflections of the Si phase. The background area C was determined using the XRD diagrams of the Si reference standard NIST 640 (Si standard = 100% crystallinity). Area B corresponds to an inserted background profile and the constant background C. Calculation (HighScore Plus software). Si standard (Standard Reference Material 640d for X-Ray Metrology, David R.Black, Donald Windover, Albert Henins, David Gil, James Filliben, and James P. Cline; National Institute of Standards and Technology, Gaithersburg, MD, 20899). In X-ray amorphous powders, there are no sharp interferences in XRPD, but only a few diffuse ones at small diffraction angles. Materials with this type of X-ray diffraction pattern are called X-ray amorphous. Crystalline: A crystal is an anisotropic, homogeneous body that has a three-dimensional periodic arrangement of its building blocks and an XRPD with clearly defined, resolvable reflections.

[0084] The invention also relates to silicon anodes comprising shaped bodies made of silicon particles, which comprise silicon primary particles, agglomerates of silicon primary particles, aggregates of silicon primary particles and / or mixtures thereof, wherein in particular the agglomerates and / or aggregates have a size of 10 nm to 200 pm (micrometers). Preference is given to agglomerates and / or aggregates in the range from 100 nm to 30 micrometers, in particular from 200 nm to 5 micrometers, preferably from 300 nm to 1.5 micrometers and / or from 400 nm to 1 micrometer. At the same time, the silicon primary particles can have a particle size distribution of 1 nm to 15 nm, in particular from 50 to 300 nm or from 100 nm to 300 nm.

[0085] According to two alternative particularly preferred embodiments, the cathode of the primary cell comprises a) manganese dioxide as cathode material, or b) the cathode of the primary cell is an air cathode and the cathode comprises manganese oxide, in particular a manganese oxide which is not manganese dioxide and optionally manganese dioxide, platinum, platinum-based, nickel-cobalt cyanide or silver as catalyst in the cathode material.

[0086] Nickel-cobalt cyanides are exemplary of the class of non-noble metal catalysts with excellent electroactivity for the oxygen reduction reaction in neutral electrolytes. The preparation of the Ni / Co-doped CN hollow nanotube composite catalysts (CN, Co / CN, Ni / CN, and Ni-Co / CN) is achieved by simple pyrolysis of the Ni / Co salt-dicyandiamide-glucose mixture. A corresponding silicon-air battery was assembled in a neutral medium using the prepared sample as the catalyst for the air electrode and demonstrated excellent discharge performance and stability.

[0087] The cathode preferably comprises manganese dioxide as a material, i.e., as a cathode material or as a catalyst in the cathode material to accelerate the solubility of oxygen. A preferred cathode material for a cathode in a primary cell with an air cathode preferably comprises manganese oxide, and optionally manganese oxide, as well as silver as a catalyst. A particularly preferred cathode material, in particular for a primary cell with an air cathode, has a hydrophobic cathode whose cathode material comprises a mixture of manganese (di)oxide, i.e., manganese oxide and / or manganese dioxide, preferably with an average particle size of less than or equal to 10 μm (micrometers), in particular electrolytic gamma-manganese dioxide, a conductivity promoter, and a polymeric halogenated hydrocarbon, in particular a polymeric fluorinated hydrocarbon, in particular polytetrafluoroethylene. The mixture can be pressed into plates and dried.In this case, a microporous, hydrophobic film, for example made of a polymeric fluorinated hydrocarbon, is preferably applied to the cathode side exposed to air in the primary cell.

[0088] A particularly preferred cathode material for the cathode, especially for a cathode in a hermetically sealed battery housing, comprises 75 to 85 wt.% manganese dioxide and 15 to 25 wt.% carbon-containing conductivity enhancer, with the total composition of the cathode material being 100 wt.%. The cathode material preferably does not yet comprise an electrolyte or is dry cathode material.

[0089] The carbon-containing conductivity enhancer preferably comprises carbon-containing particles, particularly preferably graphene-containing particles. The carbon particles preferably have a particle size distribution in the range from 0.1 nm to 5 micrometers, preferably from 5 nm to 5 micrometers. It is further preferred if the carbon particles have a particle size in the range from 5 nm to 300 nm, in particular from 10 nm to 150 nm, particularly preferably from 20 to 100 nm, and optionally are present as agglomerates with a size of 100 nm to 3 micrometers, preferably a size of 300 nm to 2 micrometers.

[0090] To produce an anode or cathode, a conductivity enhancer, silicon particles for the anode, manganese dioxide for the cathode, and optionally a binder, such as a polymeric fluorinated hydrocarbon, are mixed and optionally dried. A homogeneous particle size of less than or equal to 10 micrometers to 5 nm is preferably achieved, and the mixture is pressed into an anode (plate) or cathode (plate).

[0091] According to a further alternative, the primary cell has an air inlet at the air cathode, which can be a gas-permeable membrane. A membrane made of an inert polymer, preferably polyfluoropolyethylene, polyfluoropolypropylene, or copolymers thereof, is preferred. The air cathode is generally constructed as a sandwich structure comprising a gas-permeable membrane, a metallic mesh for conducting electricity, and at least one catalyst, particularly a porous catalyst. The gas-permeable membrane is preferably impermeable to carbon dioxide and permeable to oxygen and optionally nitrogen.

[0092] It is further particularly preferred if the anode, in particular the anode material, in particular in the charged state of the primary cell, does not comprise any lithium, preferably does not comprise any lithium ions, in the concentration range of greater than or equal to 10,000 ppm by weight, greater than or equal to 100 ppm by weight. Particularly preferably, the anode material comprises less than 10 ppm by weight of lithium atoms. Preferably, the anode material comprises less than 10 21 Lithium atoms / cm 3 Silicon particles. Furthermore, it is preferred if the concentration of lithium, in particular lithium ions, in the electrolyte is less than or equal to 10,000 ppm by weight, in particular less than or equal to 1,000 ppm by weight, preferably less than or equal to 100 ppm by weight.

[0093] It is particularly preferred if the silicon particles, in particular the primary silicon particles, are essentially amorphous (X-ray amorphous), as this ensures uniform dissolution of the silicon particles in the electrolyte. With essentially crystalline silicon, dissolution in the electrolyte would occur anisotropically. Amorphous silicon is dissolved isotropically, so that amorphous silicon can deliver a higher energy density. For example, in alkaline etchants, the etching rate for the (111) directions of a silicon crystal is approximately two orders of magnitude lower than that of any other direction. The (100)-oriented surfaces of the silicon crystal are etched one and a half times faster than the (110)-oriented surfaces. Doped, amorphous silicon particles can also be used. If the doping of p-type silicon particles is greater than > 10 19 per cm 3, the etching rate is reduced, since the higher the doping rate, the lower the etching rate. Therefore, the power density can also be adjusted via the etching rate through the doping in amorphous silicon particles.

[0094] Amorphous silicon primary particles are silicon primary particles, usually in powder or solid form, which (silicon primary particles) are X-ray amorphous and can optionally be embedded in a particle-dispersed form in an auxiliary matrix, e.g., carbon black. X-ray amorphous means that the X-ray signal, corresponding to the main peaks: 28.5° (111), 47.4° (220), 56.0° (311), 69.4° (400), reaches a maximum of less than 10% of the signal amplitudes relative to the fee structure of the silicon (JCPDS card: 00-027-1402).

[0095] The anode material according to the invention does not comprise silicides. Silicides are understood to be intermetallic compounds with a stoichiometric proportion of at least one second metal. Silicides comprise a homogeneous chemical compound of two or more metals with lattice structures that differ from those of the constituent metals. Furthermore, the anode material as a whole does not comprise a classic alloy of at least two elements that together exhibit the typical metal characteristic of a crystalline structure with a metal bond, since the silicon particles are preferably essentially amorphous (X-ray amorphous).

[0096] The electrochemical primary cell according to the invention is not a lithium-ion secondary battery. Therefore, the anode material does not comprise a lithium intercalation compound. According to the invention, the cathode material does not comprise a lithium metal oxide.

[0097] The silicon particles may comprise, at the atomic level, an alloy of silicon with at least one element of the 13th or 15th main group, wherein the at least one element of the 13th or 15th main group has a concentration of greater than or equal to 10 21 atoms / cm 3 selected from at least one electron donor and electron acceptor. The alloy of silicon at the atomic level with at least one element from main group 13 or 15 exists as an amorphous phase.

[0098] According to one embodiment, the silicon primary particles essentially have a particle size of 1 to 500 nm, in particular of 5 to 20 nm, preferably of 5 to 15 nm, or in equally preferred alternatives, the silicon primary particles have particle sizes of 20 to 200 nm or of 70 to 350 nm, in particular of 100 to 300 nm.

[0099] Furthermore, it is preferred if the silicon primary particles are in the form of agglomerates and / or aggregates of the primary particles, wherein the agglomerates and / or aggregates have a particle size of 100 nm to 200 pm, in particular of 100 nm to 20,000 nm, preferably of 150 to 5,000 nm or of 400 to 2,000 nm. The aforementioned arrangements can also be regarded as nanowires or nanonetworks. In a further alternative, the silicon particles are essentially in the form of agglomerates of silicon primary particles and / or aggregates of silicon primary particles or mixtures thereof, wherein the agglomerates and / or aggregates have a size of 100 to 30,000 nm, in particular of 100 to 5,000 nm, preferably of 100 nm to 3,000 nm, more preferably 150 to 1,000 nm, 400 to 1,000 nm or 200 to 2,000 nm.

[0100] The silicon primary particles according to the invention preferably have a surface area of ​​1 m 2 / g up to 800 m2 / g, especially from 10 - 200 m 2 / g, preferably with a primary particle size of about 10 nm on average with plus / minus 9 nm. Furthermore, the surface area of ​​the agglomerates and / or aggregates is preferably from 10 to 80 m 2 / G.

[0101] The cathode and / or the anode preferably have a porosity determined by density measurement. The porosity of the cathode and / or the anode is preferably from 18 to 28 vol.% relative to the total volume of the cathode (100 vol.%), preferably from 24 to 28 vol.%, particularly preferably from 25 to 27 vol.%. The porosity is the space in the anode and / or the cathode available for the fluid electrolyte. The porosity is expressed as a percentage volume of the total geometric volume of the cathode or the anode. Thus, the spaces formed by the porosity can be partially and gradually completely filled with electrolyte during operation.

[0102] The invention also relates to a multi-cell battery, wherein the battery comprises at least two to 15,000, in particular 3 to 500, preferably 4 to 300, interconnected primary cells. Of the two to 15,000 interconnected primary cells, 4 to 100 are preferably connected in series, and the remaining cells are connected in parallel. The battery is defined according to DIN standard 40729.

[0103] The invention also relates to the use of silicon as anode material in the form of shaped bodies of silicon particles, in particular in primary cells, which are present as silicon primary particles with a particle size between 1 nm and 3000 nm and, in particular, the silicon primary particles form agglomerates and / or aggregates or mixtures thereof, wherein the silicon particles, in particular the silicon primary particles, are optionally substantially amorphous and the anode material in the charged state does not comprise any lithium. Preferably, the anode material in the charged state does not comprise any lithium ions in the concentration range of greater than or equal to 10,000 ppm by weight, preferably greater than or equal to 1,000 ppm by weight, particularly preferably greater than or equal to 100 ppm by weight. Preferably, the anode material comprises less than 1 O 20 Lithium atoms / cm 3 .

[0104] Furthermore, the electrolyte preferably does not contain any lithium ions with a concentration in the electrolyte in the range above 10,000 ppm by weight, in particular above 1,000 ppm by weight, preferably less than 100 ppm by weight.

[0105] The gas diffusion electrode can be a membrane and / or a steel grid, preferably made of a plated steel wire, e.g., nickel-plated. A gas diffusion electrode comprising a PTFE layer, such as that from Gaskatel, can also be used. Gas diffusion electrodes can alternatively comprise membranes made of the following materials: ethylcellulose, polyphenylene oxide, polymethylpentene, modified polycarbonate, cellulose triacetate, cellulose acetate, polydimethylsiloxane (PDMS), PSDM with PC, polysulfone with PDMS, or polyimide.

[0106] The invention is explained in detail below using examples, without limiting the invention to these examples.

[0107] Examples of implementation:

[0108] Production of molded body, here sintered compact:

[0109] Mass: 1.0 g, Max. pressure: 180 bar, Max. temperature: 750 °C, Holding time: 180 s,

[0110] Furnace: Spark-Plasma sintering furnace DSP 507, Fritsch. The compacts of the exemplary embodiments were all sintered with the same parameters.

[0111] Figures 1a and 1b show an electron image of the front and back sides (without coating) of a silicon anode (P21) doped with an average of ~ 2 wt% n- and p-type doping. The following EDX-analyzed regions of the front side of the silicon anode mold are shown in the figure, some of them numbered.

[0112] Table 1a: Analyzed elements (B, C, N, O, Si, Sb) of the front side of a silicon anode according to Figure 1a.

[0113] Table 1 b: Analyzed elements (B, C, N, O, Si, Sb) of the back side of a silicon anode according to Figure 1 b.

[0114] Figures 1c (200 micrometers), 1d (100 micrometers), 1e (2 micrometers) to 1f (200 nanometers) show SEM images (JEOL JSM 7600F, Acc. 20 kV, detector: SE(I)) of the outer surface of the molded body (here: compact) without coating, as well as in Figures 1e and 1f of the outer surface and partially of the inner surface of the molded body for producing the silicon anode (with coating). In Figures 1e and 1f, the individual silicon particles, which are connected to one another at contact points and form the outer and inner surfaces of the molded body in the nanometer range, are clearly visible. The contact points between the silicon particles are formed from the material of the silicon particles melted here. A large number of silicon particles are therefore integrally connected to one another at the contact points, here fused.

[0115] Figure 1g shows a silicon layer produced using an alternative, preferred route. Silicon anode production can be achieved cost-effectively by processing silicon particles mixed with a hydrogen plasma jet. In this process, which is similar to plasma spraying, silicon particles, preferably from the processing of sawing suspensions from wafer sawing processes, are heated to such an extent that the silicon melts and can be deposited, including its impurities, onto an electrically conductive substrate (e.g., metal mesh, graphite fiber mesh, etc.). As an example, silicon layers with a thickness of approximately 20 micrometers were produced in this way, which can be used as an anode for a silicon primary battery. Silicon layers produced in this way can optionally be recrystallized using a zone melting process to achieve a good morphology.By segregating the impurities in the zone melting process, very cost-effective sawdust or recycled silicon (polycrystalline) can be used to produce silicon layers with higher conductivity, which are also characterized by a high “internal surface”.

[0116] The resulting silicon primary cell achieves performance values ​​comparable to cells with sintered anodes. This makes it particularly advantageous to manufacture anodes for high-performance cells in a roll-to-roll process using materials such as carbon fiber fabric or metal mesh.

[0117] The contact coating of the molded bodies was carried out with a gold coating. Figure 3a shows the front side (50) of the anode molded body, and Figure 3b shows the back side (51) of the silicon anode molded body coated with gold (52). For this purpose, gold was sputtered onto the back of a molded body. A compact or molded body was sputtered with eight layers of gold (Test No. 4, Table 2).

[0118] The silicon anodes thus prepared were measured in the primary cell of Figure 2c in an alkaline, aqueous electrolyte (stirred) under the following conditions (electrolyte: KOH 3 mol / L, 1 wt.% PEG 4000, molded bodies No. 1 to 6, (coating: gold, No. 4 with 8 layers of gold), electrode spacing: 2 cm, resistance over the entire cell 2.6 ohms [Ω],

[0119] Table 2: Resistance measurement

[0120] Gas (compressed air), +: 4 layers of gold leaf

[0121] The fluctuations in the (internal) resistance of the silicon anode shown in Table 2 result from varying degrees of contact between the silicon anode and the anode contact with the cable connection. It was found that both oxidized particles on the surface and surface inhomogeneities, as shown in Figure 1a to Figure 1f, can lead to fluctuating resistance values. The molded body of test no. 4 with eight layers of gold as a coating for contacting was measured under the following conditions and showed a resistance of 0.4 ohms (electrolyte: KOH 3 mol / L, 1 wt.% PEG 4000, electrolyte is stirred (magnetic fish with magnetic stir plate), molded body: coating: gold, electrode distance: 2 cm, gas at cathode: compressed air, resistance across the entire cell 2.6 ohms [Ω], primary cell according to Figure 2c). The impedance spectrum (Figure 4) of the test cell shows a resistance across the entire cell of approximately 2.6 ohms over a frequency range of 10 Hz to 100 kHz.The molded body of experiment no. 6 was measured under the following conditions and showed a resistance of 2.1 ohms (electrolyte: KOH 3 mol / L, 1 wt% PEG 4000, molded body: coating: gold, electrode distance: 2 cm, gas at cathode: compressed air, resistance across the entire cell 2.6 ohms [Q], primary cell according to Figure 2c).

[0122] This silicon anode was measured in electrolyte for 1500 seconds and the voltage and current were determined under various load conditions. Initially, the open circuit voltage (OCV) is 0.8 V without stirring the electrolyte, the full potential build-up within ~ 200 seconds and then reaches a voltage of almost 1.38 volts, which is available with stirring of the electrolyte. Afterwards, power is drawn for ~ 400 seconds at U=800 mV (without stirring), whereby a constant current flow of approx. 81 mA is maintained. After a total of 600 seconds of operation, a load change occurs with power drawn at U=600 mV (without stirring), whereby a constant current flow of 120 mA can be maintained for a further 600 seconds. In this specific case study, the silicon transfers electrons with an average power potential of 0.6V*0.12A=0.072VA=0.072Watt, thus representing an electron-supplying fuel.During this test period, no detached silicon particles from the silicon anode could be detected in the electrolyte.

[0123] In contrast, the same amount of powdered silicon (Material A and Material B according to Table 1), held between two membranes with the same electrode cross-section, dissolves after approximately 1100 seconds (Material A) or 1000 seconds (Material B). The larger surface area of ​​the silicon particles leads to a higher current and thus faster consumption. With silicon powder materials C and D according to Table 1, power could still be extracted from the cell after 2000 seconds of operation.

[0124] With a silicon wafer, only significantly lower currents could be achieved with the same electrode cross-section at an applied voltage of 0.8 volts. Depending on the thickness of the wafer, the mechanical stability of wafer silicon falls somewhere between that of silicon powder and a sintered pellet. The resulting specific power of the cell with wafer silicon is lowest due to the lower current intensity. This is due to the smaller surface area of ​​the wafer silicon.

[0125] Below are various design options for a silicon primary cell in which the silicon anode can be used. Specific measurements with the silicon anodes were performed using the primary cell shown in Figure 2c.

[0126] A cell of a silicon primary battery 1 is explained in more detail with reference to Fig. 2a: A composite electrode 5 consisting of a suitable contact plate made of copper or stainless steel as the discharge electrode, a 4 cm by 4 cm nickel mesh, preferably gold-plated, as a contact mediator between the discharge electrode and the chemically inert electrode carrier, and a chemically inert electrode carrier (preferably a graphite-polymer compound) is applied to an insulating carrier plate 3 (square polymer plate 4 cm by 4 cm). On top of this lies a 4 cm by 4 cm silicone plate 6a with a height of approximately 1 mm, which is provided with a central recess 10a (hole) with a diameter of approximately 2.5 cm. Anode material 9 (silicon granules or a paste mixture of silicon powder, conductive carbon black, water, wetting agent, and electrolyte) is preferably inserted or coated into this recess. A separator 7 (e.g. blotting paper) is placed on top of this, with a flag projecting over the 4 cm by 4 cm area.On top of this lies another 4 cm by 4 cm silicone plate 6b, approximately 1 mm high, with a central recess 10b (hole) approximately 2.5 cm in diameter. The cathode material 8 (a paste mixture of manganese dioxide powder, conductive carbon black, water, catalyst, wetting agent, and electrolyte) is then coated into this. On top of this lies another composite electrode 4 consisting of a chemically inert electrode carrier (preferably a graphite-polymer compound), a 4 cm by 4 cm nickel mesh, preferably gold-plated, as a contact mediator between the discharge electrode and the chemically inert electrode carrier, and a matching contact plate made of copper or stainless steel as the discharge electrode on top. On top of this lies another insulating carrier plate 2 (square polymer plate 4 cm by 4 cm). This so-called sandwich structure of a silicon primary cell 1 can be clamped together in a vice arrangement.

[0127] The basic structure of a preferred variant of the primary cell 1 is shown in Figure 2b. The primary cell has a silicon anode 14 and an air cathode 15. The anodes can be formed from silicon wafer plates, silicon granulate tablets, compacted powder granulate tablets, etc. Between the anode 14 and cathode 15 is a cavity 11 for accommodating an electrolyte of approximately 0.6 ml. The effective electrode area for a non-porous anode area is approximately 0.44 cm 2 (Circle with radius 0.375 cm). The silicon anodes according to the invention thus allow for a significantly larger anode surface due to the outer and inner surface provided by the silicon particles.

[0128] Fig. 2b shows a cell arrangement of a primary cell. The supply and discharge of the electrolyte with a reservoir 13 are each provided via a line 12. 2 and 3 represent contact electrodes. Between contact electrode 2 and anode 14 there is a discharge contact support spring network 16 which ensures stable, flat electrical contact between contact electrode 2 and anode 14 or between contact electrode 3 and cathode 15. When an air cathode 15 is used, the associated contact electrode 3 is designed as a hollow electrode so that air or oxygen can reach the air cathode. By way of example, a hole is shown on contact electrode 2 through which a cable for current discharge (screw with cable eyelet) can be connected. If the anode and / or cathode are fired with pastes, a separator separates the anode or cathode. The contact electrodes 2 and 3 consist of electrically conductive materials, e.g. graphite polymer compounds.These are screwed or embedded into the battery body, which is made of insulating and corrosion-resistant material, e.g. PEEK or Plexiglas. The contact electrodes 2 and 3 press on the discharge contact support spring network 16, which in turn presses on the anode 14 and cathode 15, respectively. The anode 14 and cathode 15, respectively, experience counterpressure from the electrolyte body 12 with the hollow rings 7. The discharge contact support spring network 16 compensates for the mechanical stresses that occur at the silicon anode and the (air) cathode. The reservoir 13 is not shown and can be a second hollow space in the form of a container with or without a pump. Figure 2c shows an actual structure of the test cell: 20: Anode in the form of a disk comprising silicon particles as powder in a separator or as a sintered disk made of silicon particles. Alternatively, a silicon-carbon paste can be used as an anode in the form of a disc, 21 : air cathode, 22: electrolyte reservoir (20 ml, 6 cm. 2anode and cathode surface); 23: electrolyte liquid supply / discharge line; 24: inert gas supply / discharge line (argon and / or N2); 25: cathode current collector, 26: anode current collector.

[0129] Figure 2d shows another primary cell 30, for example for a battery stack, in an exploded view. Shown are: seal 31, in particular a silicone seal or textile sealing cord, seal 32 anode, in particular a silicone seal or textile sealing cord, 33 housing, in particular for holding the anode, 34 housing part of the silicon anode, 35 cathode, here the air cathode, 36 membrane, in particular with a frame, 37 busbar for the cathode, 38 busbar for two anode cells, 39 air supply hose for the air cathode, 40, 41 air exhaust hose for each air cathode, 42 schematic representation of a reservoir for the electrolyte liquid, 43, 45 electrolyte return, 44 electrolyte supply as bottom flow. Figure 2e shows the silicon anode in a stack 49 of silicon anodes. The holder 46 of the silicon anode stack, the silicon anode 47 in the form of a rectangular plate or disc, which are arranged into a stack 49 by means of spacers 48.

[0130] The following tables show suitable silicon particles that could be sintered into compacts. Particles D are analogous to those used above.

[0131] Table 1 : X-ray amorphous silicon particles

Claims

Patent claims 1. Silicon anode, in particular for use in electrochemical primary cells with alkaline electrolyte, characterized in that the silicon anode is a three-dimensional shaped body with an outer surface and an inner surface, wherein the three-dimensional shaped body comprises silicon particles with a particle size of 1 nm to 30 micrometers, and the silicon particles are metallurgically bonded (silicon) to neighboring silicon particles at contact points, wherein the three-dimensional shaped body has a coating of a conductive metallic alloy or metal for electrical contacting on at least a part of its outer surface.

2. Silicon anode according to claim 1, characterized in that the shaped body of the silicon anode has a density of 0.1 g / cm³ 3 up to 2.3 g / cm3.

3. Silicon anode according to claim 1 or 2, characterized in that the shaped body is selected from polyhedron, sphere, hemisphere, cone, in particular selected from prism, cylinder, cuboid and cube.

4. Silicon anode according to one of claims 1 to 3, characterized in that i) the silicon particles are bonded together i) fused and / or ii) sintered and / or iii) pressed together.

5. Silicon anode according to any one of claims 1 to 4, characterized in that the three-dimensional shape of the silicon anode is a substantially flat plate, wherein the plate i) has a front and a back opposite the front, wherein the front will be facing an electrolyte and the back has at least a partial coating with a conductive metallic alloy or metal for electrical contact, or ii) has a front and a back opposite the front, as well as one or more circumferential side surface(s) connecting the front and back, wherein the front and back will be at least partially facing an electrolyte and a region of the side surface(s) and optionally a region of the front and / or back adjacent to the side surface(s),a coating with a conductive metallic alloy or metal for electrical contact, in particular the area of ​​the front and / or back side comprises 1 / 3 to 1 / 5000 of the outer surface of the front and / or back side.

6. Silicon anode according to one of claims 1 to 5, characterized in that the mass ratio of the silicon anode body to the coating is 1000000 : 1 to 10 :

1. Silicon anode according to one of claims 1 to 6, characterized in that the coating of the conductive metallic alloy or of a metal for electrical contacting comprises elements of groups 3 to 11, preferably of groups 8 to 11 and particularly preferably of groups 3 to 11 of periods IV, V and VI of the periodic table (main groups 3 to 11), particularly preferred are the elements of groups 8 to 11 and of periods V and VI, preferably are precious metals comprising gold, ruthenium, rhodium, osmium, iridium, platinum and / or silver.Silicon anode according to any one of claims 1 to 7, characterized in that the three-dimensional shaped body has an outer surface and an inner surface, wherein the shaped body comprises silicon particles, and wherein the shaped body is at least partially provided or equippable on at least a portion of its outer and inner surface, which preferably does not have a coating with a conductive metallic alloy or a metal for electrical contacting, with at least one functional silane, functional siloxane, a mixture of functional silanes, a mixture of functional silanes and functional siloxanes, and / or a mixture of siloxanes. Silicon anode according to any one of claims 1 to 8, characterized in that it comprises silicon particles with an at least bimodal particle size distribution comprising i) silicon particles with a particle size of 1 nm to 500 nm, and ii) silicon particles with particle sizes of 1 to 30 micrometers.Silicon anode according to any one of claims 1 to 9, characterized in that the shaped body comprises silicon particles and optionally particles containing carbon and silicon and optionally particles of at least one allotropic carbon modification, wherein the silicon particles, in particular the silicon anode, have an iron content of greater than or equal to 0.02 mg / kg. Silicon anode according to any one of claims 1 to 10, characterized in that the shaped body comprises silicon particles and optionally particles containing carbon and silicon and optionally particles of at least one allotropic carbon modification, wherein the silicon particles, in particular the silicon anode, each independently have an iron, potassium, zinc, aluminum, carbon, calcium, optionally titanium, optionally oxygen, optionally copper content of greater than or equal to 0.01 mg / kg.Silicon anode according to any one of claims 1 to 11, characterized in that the shaped body comprises amorphous silicon particles, mono- or polycrystalline silicon particles. Method for producing a silicon anode, in particular according to any one of claims 1 or 11. 12, encompassing the steps, - Providing silicon particles with a particle size of 1 nm to 200 micrometers, in particular with at least a bimodal particle size distribution comprising i) particles with a particle size of 1 nm to 500 nm, and ii) particles with particle sizes of 1 to 30 micrometers, a) optionally producing a composition comprising the silicon particles and at least one polymerizable monomer or a mixture of polymerizable monomers, and forming the composition into a blank of the three-dimensional molded body, and b) forming the silicon particles into a blank of the three-dimensional molded body, and - Heating the blank of the three-dimensional molded body, optionally under overpressure, and - Obtaining the three-dimensional shaped body with outer surface and inner surface comprising the silicon particles and, - Coating the three-dimensional shaped body comprising the silicon particles on at least a part of its outer surface with a coating of a conductive metallic alloy or metal for electrical contacting, and - Obtaining a silicon anode comprising a three-dimensional shaped body comprising the silicon particles, with a coating of a conductive metallic alloy or metal for electrical contact on at least a portion of its outer surface. The method according to claim 13, characterized in that the silicon particles have a content of iron, potassium, zinc, aluminum, carbon, calcium, optionally titanium, optionally oxygen, optionally copper, each of greater than or equal to 0.01 mg / kg. Silicon anodes obtainable according to the method of claim 13 or 14.Use of silicon particles comprising an iron, potassium, zinc, aluminum, carbon, calcium, optionally titanium, optionally oxygen, optionally copper content of each independently greater than or equal to 0.01 mg / kg for the production of silicon anodes comprising a three-dimensional shaped body with an outer surface and an inner surface, wherein the three-dimensional shaped body comprises silicon particles with a particle size of 1 nm to 200 micrometers, and the silicon particles are metallurgically bonded to one another at contact points with adjacent silicon particles, wherein preferably the three-dimensional shaped body has a coating of a conductive metallic alloy or metal on at least a portion of its outer surface for electrical contacting. Use of a silicon anode according to any one of claims 1 to 15 as an electron-supplying fuel, in particular for use as an electron source in an anode of a primary cell.Use of the silicon anodes according to any one of claims 1 to 15 as an anode in an electrochemical primary cell or as an anode in at least one primary cell of a multi-cell battery, wherein the battery comprises at least two to 15,000 interconnected primary cells, preferably two to 15,000 of the interconnected primary cells are in. Connected in series, preferably two to 1000 primary cells are connected in series, wherein in particular the silicon anode forms the anode in all primary cells.